The present invention relates generally to tappet assemblies for fuel injectors, and more particularly to a mechanism that maintains a tappet connected to the body of a fuel injector during shipping, handling and installation.
One class of fuel injectors used in internal combustion engines, such as diesel engines, are mechanically actuated via a rocker arm assembly that moves with each rotation of an engine""s cam shaft. The rocker arm moves a tappet downward, and a plunger underneath the tappet pressurizes fuel during the downward stroke. A spring retracts the plunger and tappet between injection events. The spring, which is always compressed, also maintains the tappet in contact with the rocker arm throughout the operation of the system. In most of these types of injectors, the spring pushes the tappet away from the injector body, but the rocker arm limits how far the tappet can be moved away from the injector body, and thus prevents the tappet from disconnecting from the injector body after installation.
During assembly, shipping and handling before the injector is installed in an engine, there is often the possibility that the tappet will accidentally disconnect from the injector body. This occurs because the tappet return spring pushes the tappet away from the injector body, and there is often no means provided for holding the tappet connected to the injector body prior to installation. In some instances, it is possible to use an external clamping mechanism to hold the tappet to the injector body prior to, and during, installation in an engine. However, in many cases space constraints during installation are so severe that no room on the outside of the assembled injector is available for retaining the tappet in the injector body. In these cases, one must either include an internal retention means or accept the risk that some tappets will become disconnected from their respective injector bodies during pre-installation shipping and handling. Oftentimes internal retention means are limited or unavailable due to internal structural and space constraints. In addition, any retention means should be either removable upon installation or arranged such that the same will not interfere with normal operation of the injector after being installed in an engine.
U.S. Pat. No. 6,209,798 issued to David E. Martin et al. on Apr. 3, 2001 shows a fuel injector having a retention member positioned in a retention opening in at least one of the tappet assembly and the injector body. The retention member limits the movement of the tappet assembly with respect to the fuel injector body. The tappet assembly disclosed in Martin has a plunger and a tappet consisting of a holder member and a plug member. The installation of the tappet assembly includes installing the retention member after the holder member is installed, but before the installation of the plug member. Improvements to the invention disclosed in Martin can be made.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of apparatus of the present application, a fuel injector has a body, a tappet, and a retention clip. The body has a retention opening therethrough. The tappet is slidably engaged with the fuel injector body and defines a retention slot. The retention clip is located within the fuel injector body and has a projection that extends through the retention opening and into the retention slot.
In one aspect of the method of the present application, a method of making a fuel injector includes providing a fuel injector body, a tappet and a retention clip as described above, inserting the retention clip into the fuel injector body such that the retention clip protrusion extends through the retention opening, and engaging the tappet with the fuel injector body such that the retention slot is aligned with the retention opening and the retention clip protrusion extends into the retention slot.